Grapevine leaf rust

Grapevine leaf rust is a grapevine disease caused by the rust fungus, Phakopsora euvitis.

Symptoms

• Small, angular yellow to brown spots on the upper surface of grapevine leaves.
• Yellow to orange, powdery spores form on the underside of the leaves.
• Affected leaves can turn yellow and die, resulting in premature leaf fall.

Plant stage and plant parts affected

Grapevine leaf rust mainly infects leaves. The fungus has also been reported to infect fruit and stems. Grapevine leaf rust can infect grapevines all year round but is most noticeable in northern Australia during the dry season.

Grapevine downy mildew can form leaf spots that are similar in size and colour to grapevine leaf rust, however downy mildew causes white, 'downy' growth to form on the lower leaf surface rather than the distinctive masses of yellow to orange spores formed by grapevine leaf rust.

Commonly found throughout east and south-east Asia (including Bangladesh, China, East Timor, India, Indonesia, Japan, Korea, Malaysia, Myanmar, Philippines, Sri Lanka and Thailand). The disease has also been reported from some grape growing areas in North, Central and South America, and Europe (Russia).

In 2001, the disease was detected in Australia's Northern Territory in backyard vines in Darwin, and has since been eradicated.

• Grapevines (Vitis species, Vitaceae), including commercial and ornamental varieties.
• Meliosma myriantha (Meliosmaceae).
• Grapevine leaf rust has also been found to infect native grapes (Ampelocissus species) under experimental conditions.

Phakopsora euvitis has 2 life cycles, and can use sexual or asexual (sometimes called vegetative) reproduction to propagate itself.

The sexual life cycle of Phakopsora euvitis is complicated, involving 3 different types of spores ('summer', 'over-wintering' and 'sexual') and the infection of 2 different host plant species (Melisoma myriantha and grapevines). The sexual life cycle can only be completed in areas where the 2 host plants, grapevines (Vitis species) and Meliosma myriantha (a tree native to eastern Asia) occur.

Typically, Phakopsora euvitis infects Meliosma myriantha in late spring to early summer, producing wind-borne aeciospores ('summer' spores). These aeciospores can then infect grapevines (Vitis species), usually from summer to late autumn. Teliospores ('over-wintering' spores) are produced on grapevines in autumn, these spores can stay dormant in dead Vitis plant leaves over the winter. In spring, the dormant teliospores germinate and the fungus undertakes sexual reproduction using wind-borne basidiospores ('sexual' spores). The basidiospores then restart the infection cycle again in Meliosma myriantha.

However, in the right environmental conditions Phakopsora euvitis can also survive by producing a single spore type on a single host plant species like grapevines, this is known as an asexual life cycle. When that happens, the fungus infects grapevines (Vitis species) and produces vegetative urediniospores. The urediniospores are able to continuously reinfect grapevines. When Phakopsora euvitis was detected in the Northern Territory in 2001, the asexual life cycle is believed to be how the fungus reproduced.

Australian grape production contributes significantly to Australia's economy, jobs and local communities. About 1,000 growers produce table grapes. In 2015–2016 Australian table grape production was valued at $431 million with exports valued at $373 million. During the same financial year, over 5,000 wine grape growers grew grapes which, once made into wine at 2,300 wineries, generated export sales valued at $2.56 billion in 2017. It is estimated that wine grapes contribute $40 billion to the Australian economy annually.

Grapevine leaf rust can cause premature leaf fall, resulting in poor grapevine health and reduced grape yield and quality.

If grapevine leaf rust were to establish in Australia, production costs would increase as a result of the need to control this disease and market access could be disrupted.

Backyard growers of grapevines would also be affected.

People illegally moving infected plant material, such as grapevine leaves, cuttings, plants and fruit, pose the greatest risk of introducing the disease to Australia. Rust spores are lightweight, windborne and easily contaminate clothing, tools, harvest and post-harvest equipment. The disease can also be easily spread on these items.

Windborne rust spores can spread the disease locally, and possibly much further.

Check grapevine plants for angular leaf spots and on the underside of leaves for masses of yellow to orange rust spores.

If you suspect that you have detected grapevine leaf rust, call Biosecurity Queensland on 13 25 23. Do not try to move the suspect grapevine material as the disease is easily spread.

Protect your farm from plant pests and diseases:

• Vineyard biosecurity manual (PDF, 2.9MB)
• Protect your farm from emergency plant pests
• Understand good farm biosecurity
• Visit the farm biosecurity website

Grapevine leaf rust is prohibited matter under the Biosecurity Act 2014.

Report suspected grapevine leaf rust to Biosecurity Queensland immediately on 13 25 23 or contact the Exotic Plant Pest Hotline on 1800 084 881.

If you think you have found grapevine leaf rust, you must take all reasonable and practical steps under your control to minimise any associated risks. This is called a general biosecurity obligation (GBO).

Because there is a risk of introducing grape phylloxera, you will need to apply for a biosecurity permit to move grape products into Queensland.

Your compliance with these regulations will help protect Queensland from serious grapevines pests and diseases.